The invention relates to a combination input and output scanner, and more particularly to a single scanning carriage incorporating a reading head and a printing head to permit substantially simultaneous reading and writing of a document original and copy thereof.
Historically, copies of document originals have been produced by a xerographic process wherein the document original to be copied is placed on a transparent platen, either by hand or automatically through the use of a document handler, and the document original illuminated by a relatively high intensity light. Image rays reflected from the illuminated document original are focused by a suitable optical system into a previously charged photoconductor, the image light rays functioning to discharge the photoconductor in accordance with the image content of the original to produce a latent electrostatic image of the original on the photoconductor. The latent electrostatic image so produced is thereafter developed by a suitable developer material commonly referred to as toner, and the developed image transferred to a sheet of copy paper brought forward by a suitable feeder. The transferred image is thereafter fixed as by fusing to provide a permanent copy while the photoconductor is cleaned of residual developer preparatory to recharging.
More recently, interest has arisen in electronic imaging where in contrast to the aforedescribed xerographic system, the image of the document original is converted to electrical signals or pixels and these signals, which may be processed, transmitted over long distances, and/or stored, are used to produce one or more copies. In such an electronic imaging system, rather than focusing the light image onto a photoreceptor for purposes of discharging a charged surface prior to xerographic development, the optical system focuses the image rays reflected from the document original onto the image reading array which serves to convert the image rays to electrical signals. These signals could be used to create an image by some means such as operating a laser beam to discharge a xerographic photoreceptor, or by operating some direct marking system such as an ink jet or thermal transfer printing system.
It is generally advantageous if the normally separate document reading and copy printing operations could be combined. If some of these reading/writing functions could be combined, system operation and synchronization could be simplified and system cost reduced through the use of fewer parts.
There are systems in the prior art that address the above identified concerns. For example:
U.S. Pat. No. 4,496,984 to Stoffel and U.S. Pat. No. 4,583,126, a division of the above-identified reference, disclose an input/output scanner for simultaneously reading a document and writing a copy. The document and copy sheet are fed in back to back relation to the read/write station. A monolithic full width reading array reads each line in two steps, to improve resolution. The writing array consists of rows of ink jet nozzles, of which the number and disposition is in direct correspondence to the sensors of the read bar.
U.S. Pat. No. 4,424,524 to Daniele discloses a full width read/write LED array for scanning a document in the read mode or exposing the photoreceptor in the write mode. A Selfoc optical fiber lens array is used for focusing the full width LED array on the document or photoreceptor.
U.S. Pat. No. 4,636,871 to Oi discloses a copying machine comprising separate reading and printing arrays and a scanning mechanism for moving the subject copy. A relative movement between the copying paper sheet and print element and between the document and read element is effected so that scanning is performed in the same pattern on both the reading and printing sides.
A difficulty with these prior art systems is the complexity and cost of separate components such as the complex optics, photoreceptor and developer in a typical xerographic process such as the Daniele system. In other systems such as the Stoffel system, it is necessary for an operator to manually combine a document and copy sheet into a single unit for manual insertion to the machine feed rolls. Such a system also has a significant cost penalty associated with components such as the monolithic full width reading array. It is an object of the present invention, therefore, to provide a new and improved read/write scanner/printer system in which a read head and print head are both substantially smaller and less expensive than a full width array component, and co-mounted on the same single scanning carriage to substantially simultaneously read a stationary document and print a copy on a copy sheet. It is another object of the present invention to provide a document that is read and a copy that is printed in a series of bands across the document and copy, that is, after each band of information is read and printed, the read and write components are indexed down the document and copy so that the next band of information can be read and printed.